NASA's Ikhana glides in for landing at the conclusion of the first checkout test flight of the new ADS-B Automatic Dependent Surveillance-Broadcast aircraft tracking technology on an unmanned aircraft system. (NASA Photo / Tony Landis) › View Larger Image

Mail and packages may one day move from city-to-city aboard unmanned aircraft systems, or UAS, flying in the same airspace as airliners, cargo planes, business jets and private aircraft. When it does, it is likely that a technology developed and flight tested at Dryden helped to make it possible.

The Automatic Dependent Surveillance-Broadcast, or ADS-B, sensor is an air traffic control technology that will be required in all aircraft traveling in the National Airspace System. However, the ADS-B coupled with other components and technology might have added benefits to UAS, said Dryden engineer Ricardo Arteaga, the system's architect. Arteaga and his team adapted the ADS-B system for UAS during the past year and recently flew it on the Ikhana aircraft.

The March research flights combined a UAS aircraft, the ADS-B sensor, synthetic vision displays and radio communications for the first time. The integration effort advances state-of-the-art air traffic observation, Arteaga said.

Engineers and technicians check the ADS-B equipment following its installation on the Ikhana unmanned aircraft. (NASA Photo / Tony Landis) › View Larger Image Arteaga began by looking at available technology. He and the team then integrated these elements with his own ideas and designed a system of hardware and software that could meet the needs of the new FAA mandates. It made sense, he explained, to start small on a UAS to determine the merits of the ADS-B device before expanding its use to larger aircraft.

Arteaga considers the ADS-B system flown on Ikhana to be the next step in air traffic control surveillance technology evolution. The ADS-B system gives a UAS a capability it doesn't currently have - to periodically transmit its own three-dimensional position and airspeed, as well as that of other aircraft in the vicinity. Only air traffic controllers currently have information on each aircraft's position. The ADB-S system could help with a future requirement for UAS - a detection and warning system to avoid accidents.

The research flights measured the accuracy of the aircraft's position information to be within 10 meters. The synthetic vision display was also evaluated in flight for its ability to provide the pilot in the ground cockpit with enhanced awareness of the aircraft's environment. The creativity required to develop the three-dimensional visualization display was one of the best parts of the work, he said.

"A working prototype was built in May 2011 for demonstrating the initial ADS-B concept feasibility using an industry standard Earth (Internet) browser. During the initial power up everything worked as expected. It took time to flush out all the interfaces, since we were developing a new ADS-B synthetic vision display," Arteaga said.

Federal Aviation Administration officials are reviewing information gathered from the Ikhana flights to determine if the ADS-B system meets FAA requirements for certification, he said. The team is confident that the flights pinpointed the aircraft's position to less than two meters during some of the test points, significantly better than the current certification requirement. Once certification is acquired, the next goal is to integrate the system onto the unmanned Global Hawk, coordinate schedules, and see if the system works as well on a mostly autonomous - and larger - UAS.

The Dryden ADS-B system could be the right technology at the right time to assist the FAA in meeting its Congressional mandates for all aircraft to use GPS position information rather than the current radar-based systems in the United States by no later than 2020.

Regarding the integration of Unmanned Aircraft Systems, or UAS, in the National Airspace System, Arteaga's timing couldn't be much better. The U.S. Congress passed a bill providing the FAA with additional funding Feb. 6. The legislation requires military, commercial and privately owned UAS to have routine access to U.S. airspace by 2015 and makes the use of aircraft such as the Predator and Global Hawk possible for a multitude of missions.

The FAA currently restricts flight of unmanned remotely piloted, or autonomous aircraft primarily to designated military airspace. However, public agencies and their private partners have a method through the FAA to obtain permission to fly mostly small, unmanned aircraft at low altitudes away from airports and urban centers.

Certificates of Authorization, or COAs, are currently required in order to fly a UAS in the National Airspace System. Dryden personnel have become adept at working with the FAA on COAs, which for example were required when NASA's Ikhana flew in support of fire fighting missions. Submitting a COA requires a lot of paperwork and effort that can take nine months or longer to secure. The time frame is prohibitive for a number of short-notice UAS missions. Arteaga said he believes his work can provide some solutions to these challenges.

The path hasn't been without its twists and turns. Arteaga understands the challenges of working with UAS first hand, as the biggest challenge for his team was integrating ADS-B with the Ikhana.

"The team spent several weeks integrating and testing ADS-B on the ground with FAA support, before testing its performance in flight. The RF (radio frequency) telemetry for data communications proved to be problematic, requiring the avionics boxes to be removed from the aircraft and sent to the lab several times before determining the proper polarities. So, the lesson here is if at first you don't succeed, but the architecture is sound, you must try and try again to make it work," he said.

"You have to be very passionate when inventing. Without passion, you can't tolerate failures. If you can't tolerate failures, you're never going to make it from concept to flight," Arteaga added.

Seeing everything work in flight made for an excellent day Arteaga said, "There's nothing like being the first. This was the first time a medium-altitude class unmanned aircraft has flown while equipped with an integrated ADS-B technology. It works as intended and I feel elated and proud to be a NASA engineer."